To verify that the peaks observed in cw ODMR near 2.1 GHz come from spin transitions in the excited state, we first studied the dependence of resonant frequencies on the magnitude of the applied magnetic field [1]}, [2]}, [3]}. The variation of resonant frequency in cw ODMR with magnetic field applied parallel to hexagonal \( c \)  axis of hBN is shown in Fig.REF c. Resonant frequency of spin transitions between \( m_S=0 \)  and \( m_S=-1(+1) \)  in the ground state starts from 3.48 GHz, and tracks to lower(higher) frequency as B increases. The excited state spin transitions have different zero field splitting of about 2.1 GHz, and
shift along the path nearly parallel to each of the ground state line, indicating the g factor of the excited state is similar to the value for the ground state [1]}.
To explain the observed resonant frequencies and their variation with magnetic field, we use the excited state spin Hamiltonian:
\(H=D_{es}(S_Z^2 - S(S + 1)) + {\mu _B}{g_{es}}{\vec{B}}\cdot {\vec{S}} + E_{es} (S_X^2 - S_Y^2 ) - A_{es}\vec{S}\cdot \vec{I},\) 
